At what volume does hearing damage begin?

Occupational guidelines treat 85 decibels averaged over an 8-hour day as the exposure limit, and each 3 dB increase halves the safe time. Normal conversation is about 60 dB; a concert runs 100 to 110 dB, where safe exposure is measured in minutes. WHO estimates over 1 billion young people risk hearing loss from loud headphones and venues.

Source: WHO Make Listening Safe (2015); NIOSH occupational noise criteria (1998)